java输入数字异常_为什么输入第一个数字时候总是出现异常???

为什么输入第一个数字时候总是出现异常???

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

import javax.swing.event.*;

import java.util.regex.*;

class EditWindow extends JFrame implements DocumentListener

{

JTextArea text1,text2,text3;

JPanel jpanel;

EditWindow(String s)

{

super(s);

setSize(200,250);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

text1=new JTextArea(1,10);

text2=new JTextArea(1,10);

text3=new JTextArea(1,10);

text3.setEditable(false);

jpanel=new JPanel();

Container con=getContentPane();

jpanel.add(text1);

jpanel.add(text2);

jpanel.add(text3);

con.add(jpanel,BorderLayout.CENTER);

(text2.getDocument()).addDocumentListener(this);

(text1.getDocument()).addDocumentListener(this);

setVisible(true);

}

public void changedUpdate(DocumentEvent e)

{

text3.setText(null);

double oper1=0,oper2=0;

try

{

oper1=Double.parseDouble(text1.getText());

oper2=Double.parseDouble(text2.getText());

text3.setText("="+String.valueOf(oper1+oper2));

}

catch(NumberFormatException ee)

{

System.out.println("产生异常");

}

public void removeUpdate(DocumentEvent e)

{

changedUpdate(e);

}

public void insertUpdate(DocumentEvent e)

{

changedUpdate(e);

}

public class Tan

{

public static void main(String args[])

{

EditWindow win=new EditWindow("窗口");

}

}----------------解决方案--------------------------------------------------------

因为你强制把字符串变成了数字当遇到不能转变的情况就会抛出异常了